an EE disaster? back at the sophomore days, some senior students were building/fixing/something their robot at a regular empty classroom. of course they messed up and caused a power failure in the building. don't ask me what they were working on, i only saw the smoke coming from 2 doors away from the lab in which we all cursed to insanity because of data loss in our computers.
luckly nobody got hurt, but there were some nasty carbonized spots on a few desks.
those are 2 disasters in one
1: whoever made the electrical plans for the 5 story building (something like 200 classrooms and a few offices) sucks. whatever short circuit at an end point shouldn't kill all of the building power
2: having well equiped and protected laboratories, why in blazes where they working on a regular classroom?
every eletromechanical student is a series of weird short circuits waiting to happen

Let's not forget the fiasco of the original primary mirror on the Hubble Space Telescope, which was ground to the wrong shape and had to be replaced later by shuttle astronauts.
I have also heard rumors of a satellite that was launched, and during on-orbit checks, the command to power down was sent, but the craft never responded to a later command to power up again. When the same command sequence was tried on the Engineering Model back here on Earth, the same thing happened. Somebody apparently got over-zealous in deciding which circuits responded to the power down command.
But again, that's just a rumor I've heard, on and off over the years :)

"Indeed, introducing yourself as an engineer at a party likely won’t earn you the admiring ooh’s and ahh’s that, say, a fireman, or U.S. Navy Seal might get."
Hey Sylvie! Speak for yourself! I'd infinitely rather hear from an enthusiastic EE who is doing fun work, at a party, rather than a fireman. Sheesh.
Okay, so for EE disasters, e.g. the ones that would really make me pucker, are for instance a ship running aground, or colliding with another ship, because of a design fault in the control systems. Ditto, obviously, with airplanes.
Or cases of "friendly fire" caused by faulty identification hardware or software.
Take for example the disaster of that Air France flight over the Pacific, a couple of years ago. That was reportedly caused by sensor failure that gave the automatic controls the wrong instructions. Could a human pilot be trained to notice the problem? Most likely yes. But more to the point: could the control system be designed to accommodate that type of sensor failure?
These are the things that might keep EEs awake.

Nothing beats the Mars mission with metric / US unit interchange - no loss of life, but lots of lost prestige, etc.
Always remember, as engineers, the world does revolve around us. We pick the coordinate system. (Stolen from somewhere, I forget where.)

The wikipedia article to which the above link refers, says: "The engineers employed by Jack D. Gillum and Associates who had approved the final drawings were convicted by the Missouri Board of Architects, Professional Engineers, and Land Surveyors of gross negligence, misconduct and unprofessional conduct in the practice of engineering; they all lost their engineering licenses in the states of Missouri and Texas and their membership with ASCE."

Many, many years ago, when I worked for AST Research, I developed a motherboard ASIC that was basically a "garbage can" of the random logic. After the systems were in high-volume production for more than a year, there was a particular legal software title that would not "beep" correctly when some kind of event occurred, due to a subtle bug in my design. I've never held lawyers in high regard, so I thought it was kinda funny that I was able to jab a bunch them with my screw-up.

I was changing a light fixture in my bathroom over the sink and all was going well until i began connecting the new fixture. The new fixture was larger than the old one and was blocking the light from the tub so I couldn't see the screws for the connections. I got down from the sink and instinctively flipped on the light switch. I climbed back up on the sink counter and started making the connections until I touch both wires. My wife heard 2 load bangs. The first was when I flew across the room and hit the shower wall, the second is when I dropped and hit the tub. I now always place tape over the switchs when I do electrical work at home.